Tired of crummy gas and leaking needle & seats

Rubber o-rings? Here is table for methane (methanol not listed but probably same) . Same as gas except last one, 1 is best 4 is not recommended :

Perfluoro-
elastomer 1

Viton
Extreme 1

Aflas
TFE/P 2

Viton
FKM 1

EPDM
P.C. 4

Buna-N
NBR 1

Silicone 4

Fluoro-
silicone 2